Organocatalyzed (4+2) cycloadditions (Diels-Alder reactions) are reviewed in this manuscript.
Among the different catalytic alternatives, reactions involving α,β-unsaturated ketones and
alkenes are considered. In these processes, substituted cyclohexanones are obtained via HOMO activation
generated by amine organocatalysis that generate transient dienamine species. Both concerted and
stepwise mechanisms are described. In most cases, excellent regio-, diastereo- and enantiocontrol have